EVEN A CURSORY reading of the wall text at the National Gallery of Art's "Irving Penn: Platinum Prints" makes it clear that this show is as much about process as finished product. Heck, the title alone leaves no doubt about that.

But one needn't rely on labels alone. The control, clarity and tonal range of the platinum photographic print-making process, in which patterns and textures rise to the surface in the medium's subtle range of contrast, are there in front of your eyes as well. They're there in the loose threads of a rug under the painter Marc Chagall; in the wrinkled, parchmentlike skin of the writer Colette; and in the caked-clay masks of "Three Asaro Mud Men, New Guinea."

No mere retrospective of Penn's ethnographic studies; fashion photography for Vogue magazine; portraits of artists, rock stars, hippies and the intelligentsia; or of still lifes composed of trash and studio detritus, "Irving Penn: Platinum Prints" is, rather, a celebration of the artist's mastery of an at-once arcane, labor-intensive and exquisitely rewarding picture-making technique, here spotlighted in a collection of images culled from recent gifts by the artist of 85 platinum/palladium prints and 17 collages made from discarded test strips.

Of the works on view, these collages (though "scrapbooks" seems a better word) are interesting most as ways of gaining insight into Penn's creative process, as opposed to stand-alone works of art.

It is all too easy to overlook Penn's artistry for his craftsmanship, particularly because many of these images are among Penn's most famous works, albeit not always this beautifully rendered, especially in their original magazine reproduction, which tended to flatten and eliminate detail. The rich, deep shadows, seen in Penn's meticulously hand-mixed and hand-brushed emulsions of platinum mixed with palladium salts, which forgo pure blacks for areas of warm, velvety darkness, are satisfying from a technical standpoint.

Let's not forget, though, that Penn was more than a technician. The sharpness with which we can see sculptor David Smith's battered thumb -- it literally looks chewed up -- enhances our reading, not just of the subject's chosen profession, but of his character. It's worth noting that Penn referred to his portraits as his attempt to make an "incision" into the facade of the sitter. The seemingly greater depth of the platinum-print process facilitates the impression that we are going not just closer to the surface, but just a little further inside the subject.

Although Penn justified his in-studio ethnography work by explaining that he was consistently disappointed by pictures of people in their natural surroundings, there is nevertheless something about his artificially composed photographs of primitive peoples in front of seamless backdrops that is uncomfortably close to the natural history museum dioramas of old, minus the fake shrubbery.

It is, however, as much a measure of his need to control what he was taking a picture of as was his habit of photographing flattened cigarette butts, not on the streets where he found them, but in the laboratory-like environment of his studio.

Nothing wrong with control, of course. The impression that "Irving Penn: Platinum Prints" leaves you with, however, is not one of spontaneity, but of deftly reordered (one might even say stately) chaos. Rather than the "decisive moments" of a Henri Cartier-Bresson, who might be compared to a hunter, Penn's art, like that of a sculptor, is about the deliberate imposition of an external, though powerfully well-made form.

IRVING PENN: PLATINUM PRINTS -- Through Oct. 2 at the National Gallery of Art, West Building, Constitution Avenue at Sixth Street NW (Metro: Archives-Navy Memorial). 202-737-4215 (TDD: 202-842-6176). www.nga.gov. Open Monday-Saturday 10 to 5; Sundays from 11 to 6. Free.

Public programs associated with the exhibition include:

Sept. 12 and 19 at 1, and Sept. 23 and 28 at noon -- Gallery talk.

Irving Penn captures writer Colette, above, in 1951's "Colette, Paris." In his portraits, Penn tried to make an "incision" in his subjects.At the National Gallery, Irving Penn's "Woman With Roses (Lisa Fonssagrives-Penn in Lafaurie Dress), Paris," 1950.Penn's composed ethnographic photos, such as 1965's "Gypsy Family, Estramadura, Spain," have a "natural history museum" feel.